A 7 day old baby, born at term, presented to the neonatal unit with a history of vomiting with each feed and 10% weight loss (birth weight 3270 g). The vomiting started soon after birth and it was described by the parents as being projectile; it occurred during or after feeds and was non-bilious. The baby was dehydrated on admission, with dry skin and mucous membranes, but was otherwise well. Clinical examination was otherwise unremarkable including no visible peristalsis and no masses palpable. The parents interacted appropriately with the baby and there were no causes for concern among the nursing or medical staff. Initial capillary blood gas analysis showed a metabolic alkalosis.

Questions

1 What is the differential diagnosis?

2 What is the main diagnosis to exclude, and what are the main biochemical features?

3 What investigations would you perform to diagnose this?

4 What other investigations may be needed?

5 What is the most common cause of vomiting in a child this age?

Answers

Short answers

1 The most common causes in a baby are regurgitation, gastro-oesophageal reflux, hypertrophic pyloric stenosis, pylorospasm, and necrotising enterocolitis.1 Necrotising enterocolitis is more commonly seen in preterm infants but can occasionally be seen in term infants. Also consider extraintestinal causes including sepsis, drugs or other toxic agents, intracerebral abnormalities, metabolic problems, renal pathology, and medical conditions such as kernicterus.12

3 Ultrasound scanning is commonly used because it is non-invasive, does not use radiation, and can differentiate between several diagnoses—in particular, hypertrophic pyloric stenosis, gastro-oesophageal reflux disease, and duodenal anomalies. Capillary blood gas analysis and measurement of urea and electrolytes can also …